Refining of petroleum oils



Mmh 24, l193.16. H. G. SMITH 2,035,349

REFINING OF PETROLEUM OILS Filed Miy 2, 1932 5 Sheets-sheet 1 SETTLING PHNS 11616070491/- GHS rre/13th,

REFINING OF PETROLEUM OILS Filed May 2, 1932 3 Shee'r,:s-Sheec.` 2

OVERHEAD CYLINDER l/NPRESSABL RESIDUUM 66 FTS.

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FIRE AND'STEAM CLAY caNTACr/Nq REDucTloN STILI. AND

REDucr/o/v sr/LL NAPH THA NEUTRAL OILS DIST/L LA TES Reuver/ou s'r/LL CLAY FILTERS FINISHED BRIGHT sTocK Herschel Gnufh,

March 24, 1936. H G SMH-H 2,035,349

REFINING oF PETROLEUM'OILS Filed May 2, 19512 3 Sheets-Sheet 3 Rsoucso OKLAHOMA cRuas ao ws mz/'o aF.

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@w KPMMwMMM A Patented Mar. 1234, 1936 PATENTv oFFlcE 'REFIMNG oF PETROLEUM olLs Herschel G. Smith, Swarthmore, P a., assigner, by mesne assignments, to Gulf Oil Corporation of Pennsylvania, Pittsburgh, Pa., a corporation of Pennsylvania Application May 2, 1932, Serial No. 608,819

` 1s claims. (ci. 19e-4o) This invention relates to refining of petroleum oils; and it comprises a processl of refining petroleum oils for the production of lubricating oils for example, the said process including'acid treat- 5 ing such oils in at least two different steps and at two different temperatures, at least one of said treatments being conducted at temperatures ranging from 130 to 212 F.; the said process lalso Y advantageously including a step of de-acidifying lo the acid oil derived from one of said acid treating steps by simple heating and reduction; all as more fully hereinafter set forth and as claimed.

Inthe recovery of lubricating oils from various crudes, the refining step has always contributed l5 a large proportion of the expense. In spite of much time and effort spent to develop better methods, the refining process generally employed is treatment 'with concentrated sulfuric acid, often followed by washing with water and caustic 20 soda solution. The sulfuric acid treatment improves the quality of the oil, especially as regards color and odor. The treatment is usually conducted at temperatures in the neighborhood of '70,110 F. Temperatures much above this have 2.', been reported as producing dark colored and inferior products. l In the sulfuric acid process of refining, a socalled acid sludge is produced which is usuallyl separated from the remaining oil by the addition 30' of a small proportion of water followed by gravity settling, etc. The sludge-free oil retains an a'ppreciable content of acid compounds which must be removed in some fashion. The step of deacidifying this acid oil (usually Icalled sour- 35 oil) often presents considerable difficulties.

OneL of the customary methods of handling such acid oils includes washingwith water and neutralizing with a dilute caustic solution during agitation with air or steam, usually followed by 40 another washing with water. Another method which may be used is described in my copending application, Serial No. 596,093, filed March 1, 1932. This method consists in a clay contacting and reduction step at a maximum temperature 5 of about 300 to 550'F.

ils

While it has generally not been considered comsimple heating which may be accompanied by reduction. By acid treating in two different steps and at two different temperatures, at least one of saidtreatments being conducted at temperatures of 130 to 212 F., I have found an important 5 improvement in the quality of the refined oil both as to color and carbon residues.

Where lubricating oils are to be produced from a crude at some distance from the oil fields, preliminary acid treatment at or near the oil fields l may prove commercially advantageous due to lessening in bulk occasioned by such a treatment. This lessened bulk reduces the transportation costs on the oil of value, as well as the cost of the subsequent reduction. It may also happen l that the acid is cheaper' at the oil fields or that the fuel .oil sludge produced during acid treatl ment is more disposable at thalrpoint.

I have found that a more advantageous method of de-acidfying the acid oil resulting from the, above acid treating steps consists in simply passing the oil into a still and Iheating to tempera,- tures ranging from about 500 to 650 F. Reduction can be accomplished simultaneously if de-l sired. It is sometimes advantageous in thisprocess to heat the oil rapidly while in turbulent flow. This reduces the opportunity for acid sludge particles to deposit in the still in the form of coke, causing difficulty in the still. This type of heating can be accomplished in the modern tube still, for example, in which the time of heatingto temperatures above 400 F. can be restricted to less than 30 minutes. The stillcan be equipped with a fractionating tower in order to separate the lighter fractions while the heated oil is being de-acidified. If desired, the acid oil can be partially or wholly neutralized with caustic soda, for example, before being introduced into the reducing still. If the acid oil is one derived'from acid treating an unreduced crude such a neu- 40 tralizatin is often advantageous. During de-l acidification by heati g,'the color of the oil is not appreciably impa ed. Some of the color produced may be removed by simple filtration.

The described method of de-acidifying acid 01145 represents a great simplification over prior methods. Much of the mechanical handling of the Y oil is eliminated and any tendency towards the formation of troublesome emulsions is obviated.

The double acid treatment of my invention, 5o one of said treatments being at a higher temperature than the other, is advantageous in produc' ing lubricating oils of .low carbon residue and of excellent color characteristics. If desired the second treatment may directly follow the rst although better results are usually secured with the use of a heat treatment and reduction oi' the acid oil after the iirst acid treatment. At least one of these treatments (usually the second) should be conducted at elevated temperatures ranging from 130 to 212 F. while the other may be carried out at the usual temperatures of 60 to 130 F. If desired, a dewaxing step may follow each acid treatment or only the iinal treatment. By such a combination of acid treatments high grade lubricating oils can be produced even from many low grade, asphaltic base crudes.

In order to illustrate my invention more speciiically four embodiments will be described in connection with the accompanying drawings which represent four ow sheets of actual fullscale operations within the scope of my invention, wherein various petroleum stocks are treated by a series of successive operations with the ultimate production of finished bright stocks. 'I'he several operations are indicated on the iiow sheets by appropriate legends. In this showing:

Fig. 1 represents a process wherein a light crude is directly acid treated at low temperatures followed by a second treatment, after de-acidiiication by heating and reduction, at higher temperatures,

Fig. 2 represents the processing of a light, reduced crude stock with two acid treatments at diierent temperatures.

Fig. 3 shows the treatment of a heavy lubricating stock derived by mixing an unpressable distillate, an overhead cylinder stock and a residuum, while Fig. 4 shows the treatment of a very heavy residuum, which comprises an initial high-temperature treatment followed by a lower temperature treatment, after de-acidication by simple heating.

Starting at the top of the ow sheet of Fig. 1 a crude of fair quality (100 parts) is shown to be acid treated, at a temperature ranging from to F. with a quantity of 98 per cent sulfuric acid amounting to about 0.5 pound per gallon. In this process the loss of sludge was about 10 per cent. The acid oil from the acid treatment was, in this case, partially neutralized by adding 2.5 per cent by volume of 4 per cent caustic soda solution. (If desired, this step can be omitted.) No water settling of sludge was employed in this case, as the oil was of low viscosity and the soft sludge separated and settled readily.

The partially neutralized acid oil was fed, as shown, directly into a continuous tube still in which it was subjected to a re and steam reduction. Most of the charge (65 parts) was distilled ofi and recovered as gasoline, kerosene, gas oil and pressable distillates, leaving bottoms amounting to 24 parts. The latter were subjected to a second acid treatment at the higher temperature of 140 to 150 F. In this case l pound of sulfuric acid was used per. gallon of bottoms. But the loss to sludge was only 3 parts.

The acid oil derived from the second acid treating step is capable of-'being processed in several ways. As shown on the chart in dotted lines the acid oil can be de-acidled by simple heating and reduction. 'I'he maximum still temperature used in such a step is about 550 F. A small yield of distillate (1 part) is obtained during reduction. After the de-acidication step it is convenient, as shown, to add the naphtha required in the subsequent wax removal operation. This dilution assists in the clay filtration which advantageously follows the step of de-acidication by simple heating. After this ltration the remaining steps followed through in the operation shown in Fig. l consisted of the usual chilling, centrifuging, reduction and clay filtration, these steps forming no part of the present invention. 5

Several other methods can be employed for deacidifying the acid oil from the second, hightemperatui'e acid treatment. One such method, namely, a clay contacting and reduction step, is illustrated on the flow chart. As there shown in 1. full lines, lime and fullers earth amounting to 0.05 and 0.6 pound per gallon of acid oil, respectivelyl can be added to the oil. The acid oil can then be heated under agitating conditions with slight reduction to a maximum temperature 15 of 550 F. The oil and clay mixture is then cooled to temperatures about 250-300 F. and passed through filters for clay removal. After filtration the steps of chilling, centrifuging, etc. are followed as before.

The process illustrated in Fig. 2 is quite similar to that of Fig. l, with the exception that in this operation a light reduced Oklahoma crude was employed. tarting at the top of this figure a reduced crude (100 parts) was first acid treated with 1 pound per gallon of 98 per cent sulfuric acid. In this operation treatment was conducted at a temperature of 104 to 123 F. The acid sludge was settled for about 5 hours, air blown for 1 hour at 135 F. and again settled for 6 hours. The acid oil was then drawn off and subjected to a simple heat treatment and reduction at a maximum temperature of around 600 F. for de-acidication purposes. In this reduction both gas oil and pressable distillates were recovered. If desired the bottoms recovered in this de-acidication step can be dewaxed before as well as after a second acid treatment. However, I usually prefer to dewax in a single operation after the second acid treatment as shown on the chart when the amount of wax present is not abnormally great.

The bottoms from the above reduction, amounting to 42 parts, were treated under agitating conditions with about 0.75 pound of 98 per cent acid 45 per gallon at temperatures ranging from 143 to 154 F. After completion of the reaction, the mixture was diluted with about 10 per cent by volume of heavy, uncracked kerosene distillate. 'I'his addition reduced the viscosity and enabled the rapid subsidence of the sludge which was removed by settling, air agitation, and again settling. The acid oil recovered from these operationswas subjected to a clay contacting and reduction step using 1 pound of clay per gallon and a Amaximum temperature ofabout 600 F. The kerosene which was added in the treating step as Well as a small amolmt of intermediate distillate were 4recovered during this reduction. Further processing included the addition of naphtha, chilling, dewaxing by centrifugal force and clay illtering.

The bright stock recovered from this processing was found to have the following characteristics:

Gravity: A. P. I 24.3. Viscosity, S. U. V.

210 Flash, open cup: F 495 Fire, open cup: F 570 Pour test: F +15 Color, N. P. A 5.5 Carbon residue: 1.4 Acid number 0.01

Figure 3 shows the reiining of a mixed lubricat- 75 ing stock comprising an unpressable distillate, an

overhead cylinder stock and a heavy residunm. One of the more important ways inwhich this process differs from that of Fig. 1 is in the dilu'- tion of the lubricatingl stock with about 12 per cent ofl heavy kerosene distillate prior to acid ture to aid in the subsidence of the sludge.

The finished bright stock produced by the opi erations outlined was found to have the following characteristics:

Gravity, A. P. I 22.8' Vis. 210 F 153 Flash, P. M. 515 Flash, O. C. 550 Fire, O. C 640 Pour, F +20 Color, N. P. A 7 Carbon residue 1.7

The process shown in Fig. 4 is of a quite different type from that shown in Figs. '1, 2 and 3. In this operation a heavy residuum from Oklahoma crude, having a viscosity of 180 S. U. V. at 210 F. was initially treated with a small quantity of acid amounting to only 1-5 pounds per barrel of the residuum. This treatment was conducted at tem'- peratures from 170200 F. The sludge produced in this treatment settled readily, leaving a warm oil practically free from acid and containing only a few particles of ne suspended sludge. In this instance the acid oil was merely cooled to the temperatures required in a second acid treating step without de-acidification, as shown in full lines on the flow sheet. An alternative procedure is to digest the acid oil in a still in order to de-acidify the same at temperatures in the neighborhood of 500 F., following the dotted lines on the chart. During such a digestion a small dis'- tillate (l part) is recovered, as indicated.

.'I'he next step of the above process was a second acid treatment with a larger proportion of acid amounting to about 1.75 pounds per gallon of the pretreated oil. This treatment was conducted at the-lower temperatures of to 150 F. After separation of the sludge, amounting to 24 parts, the resulting acid oil was subjected to a clay contacting andA reduction step for de-acidication. 'Ihe remaining process steps shown on the chart are conventional.

The finished brightV stock produced by the processing of Fig. 4 was found to have the following characteristics:

Gravity f- 23.0 Vis/210 mash, o. c 51o Fire, O. C 590 Pour: F --.+15 Color: N. P. A 6 Carbon residue: -1.75

In the two specific embodiments shown in Figs. l and 2, the first acid treatment was conducted with a relatively light product, that is, with a light crude or a light,lreduced crude. In the process of Fig. 3 a heavy lubricating stock was employed, but this stock was diluted with a light distillate prior to acid treatment. The processing of the diluted mixture was then conducted in a manner somewhat similar to that employed-in treating the stocks of lower viscosity. T'he processes shown in Figs. 1, 2 and 3 are suitable for use with light crudes, light reduced crudes, diluted heavy residua or with other stocks of similar properties. For such stocks the dual treatment method of my invention'is usually conducted by employing an initial treatment at moderate temy peratures of say 60 to 130 F. and a nal treafment at higher temperatures ranging from about v 130 to 212 F.

The dual method of treatment shown in Figs. 1, 2 and 3 has several important advantages, especially when oils are used with which the total treating losses are high. The amount of acid sive losses are obviated by adding acid in the primary treatment only suilcient to remove the bulk of the total asphaltic matter. This leaves in the acid ol not only some colloidal particles of acid sludge' but also some sulfonated compounds in solution. De-acidicatlon' of this acid oil by heating to'temperatures of. at least 500 F. is often important in that both types of these impurities are thereby decomposed'to form` materials of a secondary nature which respond read--A ily to aA subsequent acid treatment.

The double Aacid treatment of my invention, when employed with an intermediate heating step produces a product of higher quality than either a single acid` treatment with the full amount of acid or a double treatment without the intermediate heating -step. Moreover, the acid oil appears to be so conditioned by'the indesirable quantities. Inmy process theseexcestermediate heat treatment that a given amount of considerably higher lquality than that which would be produced by the use of the full amount of acid in a single treatment. The sludge setties more cleanly.

In the dual method of -acid treatment as shown in Figs. 1, 2 and 3, a large proportion of the asphaltic material is removed by the primary treatment. During the secondary acid treat--V ment I have found that superior results are usu ally obtained, as regards agglomeration and settling of sludge particles, by the expedient of adding up to 12 per cent of kerosene distillate to the agitated oil-sludge mixture after the reaction of the acid with the asphaltic and resinous4 materials hs been substantially completed. Such a procedure is shown in Figs. 2 and 3.

The flow sheet of Fig.v4 shows a somewhat different method of treating heavy lubricating stocks.' In this method of treatment such stocks areA acid `treated without the preliminary diluition shown in Fig. 3. The process is applicable to very heavy residua or to mixturesof such residua and heavy distillates, such as overhead cylinder stocks.v vIn treating this type vof oils without preliminary dilution the temperature conditions ofthe two treatmentsoutlined above are advantageously reversed.. For example, a small amount of acid may be employed. in the first treatment at temperatures ranging from 130 to 212 F. This removes a largeproportion of the asphaltic material in the form of a very stiff heavy sludge containing little or no free acid. which can be removed from an agitator after settling while-still warm, in a melted condition. A small amount of acid will remove several times its weight of asphaltic material under these conditions. Upon cooling, this sludge usually hardens to a brittle mass which can be conveniently burned in lump form on an ordinary furnace grate, acting somewhat similar to bituminous coal. Very little sulfonation is produced in this initial treatment due to the effect of mass action of the large excess of asphaltic matter and the small amount of acid used, and very little free acid or sludge particles are left in the warm acid oil. 'I'his makes it possible to conduct the second acid treatment at lower temperatures without the necessity of'an intermediate de-acidication step.

In this type of treatment only relatively small quantities of acid, for example less than one pound per gallon, should be employed in the first treating step, since, if all or a large proportion of the acid required for complete refining were added in one step, a violent reaction would ensue with the formation of undesirable reaction products and a severe loss of oil. The second treatment should be conducted at lower temperatures in order to avoid similar difficulties. A larger quantity of acid is usually used in this second treatment.

Various changes may be made in the specific steps of the processes outlined above without departing from the scope of my invention. For example the proportions and concentrations of acid used in the treating steps, the temperatures employed in the acid treating and reducing steps, the proportions of naphtha employed in dewaxing, the amount of fullers earth used, etc.. may all be varied to a considerable extent. Even the sequence of several of the steps of my process may be altered in some cases. Other variations from the above procedure which fall within the claims will be evident to those skilled in the art.

What I claim isz- 1. In the recovery of lubricating oils from heavy petroleum oils, a process of refining the lubricating oil which comprises in combination the steps of treating the oil with concentrated sulfuric acid whereby a part of the acid reacts with the oil to form a removable sludge and of deacidifying the acid oil solely by heating it to temperatures between 500 and 650 F.

2. In a process of refining petroleum oils, the step which comprises de-acidifying the acid oil derived from a sulfuric acid treatment solely by a simple heating to temperatures ranging from 500 to 650 F., the duration of said heating at temperatures above 400 F. being not greater than 30 minutes and said heating being conducted under conditions of turbulent flow.

. 3. In the recovery of lubricating oils from various stocks the rening steps which comprise treating such a stock with concentrated sulfuric acid, de-acidifying solely by heating the reaction products to temperatures between 500 and 650 F. and again treating said stock with sulfuric acid having the same concentration as used in the first step.

4. In the refining of petroleum oils the steps which consists in treating an oil with sulfuric acid, de-acidifying the acid oil solely by heating to temperatures of at least 500 F. and again treating the deacidifled oil with sulfuric acid.

5. In the recovery of lubricating oils from petroleum oil, the rening Asteps which comprise treating an oil with approximately 98 per cent concentrated sulfuric acid at ordinary operating temperatures, de-acidifying the acid oil thereby produced solely by a heat treatment at temperatures between about 500 and 650 F. and again treating with 98 per cent concentrated sulfuric acid at temperatures between 130 and 212 F.

6. In the recovery of lubricating oils from petroleum oil, the refining steps which comprise treating an oil with sulfuric acid of concentration approximately 98 per cent H2SO4 by weight at temperatures between 130 and 212 F., cooling and again treating at lower temperatures with sulfuric acid having the same concentration and de-acidifying the resulting acid oil solely by heating to temperatures between 500 and 650 F.

7. In the recovery of lubricating oils by the rening of light reduced crudes and diluted heavy reduced crudes, the three steps in combination which consist of treating such a crude with concentrated sulfuric acid at temperatures ranging between 60 and 120 F., with separation of sludge deacidifying the acid oil by heating to temperatures of from 500 to 650 F. and again treating at temperatures ranging from 130 to 212 F. with a somewhat smaller proportion of concentrated sulfuric acid having the same concentration as that used in the first step.

8. The refining steps of claim 7 in which the reaction mixture resulting from acid treatment is diluted with a light distillate in order to facilitate the settling of the acid sludge formed.

9. In the recovery of lubricating oils by refining heavy reduced crudes and petroleum residua, the steps which comprise initially treating such stocks at temperatures from 130 to 212 F. with a small proportion of the total amount of 98 per cent concentrated H2804 ultimately required for refining to the degree desired, de-acidifying the treated oil solely by heating to temperatures of at least 500 F. and subsequently treating the de-acidified oil with a proportion of 98 per cent concentration H2SO4 sufficient to refine it to the degree desired at ordinary operating temperatures.

10. In the recovery of lubricating oils by the rening of reduced crudes, the steps which comprise treating such a crude with concentrated sulfuric acid of concentration about 98 per cent H2SO4 by weight at temperatures between 60 and 130 F. in a proportion of about one pound sulfuric acid per gallon of crude, deacidifylng and reducing the acid oil by heating to maximum temperatures of between 500 and 650 F., again acid treating at temperatures of from 130 to 212 F. using somewhat less sulfuric acid of the same concentration, and finally de-acidifying the acid oil by a combined clay-contact and reduction step.

ll. In the recovery of lubricating oils by refining heavy lubricating stocks the steps which comprise diluting such a stock, treating said dlluted stock at temperatures between 60 and 130 F. with concentrated sulfuric acid of concentration approximately 98 per cent H2SO4 by weight in the proportion of 0.75 pound of sulfuric acid per gallon of stock, deacidifying by reducing the acid stock at maximum temperatures between 500 and 650 F., treating the reduced stock with concentrated sulfuric acid of the same concentration at temperatures between 130 and 212 F.. diluting the reaction mixture with a light distillate to promote settling of acid sludge. separating the sludge and de-acidifying the treated oil. 12. In the recovery of lubricating oils by the refining of heavy reduced crudes, the steps whichv comprise treating such a crude at temperatures of about 130 to 212 F. with concentrated sulfuric acid of concentrationapproximately 98 per cent H2804 by weight in the proportion of fteen pounds of acid per barrel of crude, deacidifying the acid oil by heating at maximum temperatures of from 500 to 650 F., again treating withconcentrated sulfuric acid of the same concentration at somewhat lower temperatures and de-acidifying said treated stock.

13. In the recovery of lubricating oils by the refining of heavy lubricating stocks, the steps comprising treating such a stock at temperatures ranging from 130" to 212 F. With approximately 98 per cent concentrated sulfuric acid in proportion less than one pound of acid per gallon of stock, separating the resulting sludgel cooling to temperatures ranging from 60 to 130 F., treating at these temperatures with a larger proportion of approximately 98 per cent concentrated sulfuric acid and de-acidifying the resultant acid oil product by heating to temperatures of at least 500 F.-

HERSCHEL G. SMITH. 

